In commercial fishing operations, it is preferential to store the fish catch at a temperature that is deemed satisfactory to preserve the fish and retard spoilage. Conventionally, the fish are caught, killed, generally by any one of a number of operations, and stored in a cold hold at a temperature hovering around the freezing point of water (32° F.). Innumerable freezing methodologies and freezer types are known in the art, and typical freezers include plate freezers, blast freezers, tunnel freezers, spray brine freezers, and so forth. These freezers can be used with varying degrees of success to preserve the fish during and after the fishing voyage.
In recent years, farmed fish can become commercially more successful than fish caught in the wild. Generally, commercially farmed fish have been found superior to wild fish, notwithstanding the more favorable commercial impression that wild fish enjoy in the market. Although wild fish are generally believed to have a superior flavor and texture if cooked immediately after catching, in practice, by the time the fish are sold into the food markets, it is frequently the case that the quality of the wild fish catch has deteriorated substantially. The reasons for such deterioration are typically due to the lack of sound fishing techniques in the industry, many of which techniques are known but for various reasons not practiced commercially.
For instance, fish are known to decay and develop bad flavors and odors for a number of reasons. Often, when caught, the fish is subjected to substantially stressful conditions which causes the release of hormones. This hormone release is believed to contribute adversely to flavor and odor. For this reason, the prior art teaches to stun the fish prior to killing the fish to mitigate against the release of such hormones. Typical stunning methodologies include concussively shocking the fish or treating the fish with a stunning gas, which may be any inert non-toxic gas that displaces dissolved oxygen in ambient water.
Many fish, especially salmon, are known to be covered with a mucosal layer, also called a “slime” layer, while alive. The mucosal layer is believed to protect the fish from microbial attack and from passage of salts and other electrolytes. In many conventional fishing operations, fish are handled quite roughly while in an unfrozen state. Such conventional handling techniques can disrupt or destroy the mucosal layer over substantially the entire fish, thereby leaving the fish more susceptible to passage of salt into and out of the fish and to microbial degradation. Such handling also can lead to bruising of the fish and loss of scales, and can also lead to the loss of bone, protein, and other commercially valuable parts of the fish.
It is also known in the art that oxygen can lead to decay of the fish after death. For this and other reasons, it is known to bleed the fish upon death (or to cause death) to thereby remove the blood and consequently the oxygen carried by the blood. Bleeding is also believed to cause metabolic processes within the fish to cease. Likewise, for this reason it is known to glaze the fish after freezing, i.e., to coat the fish with a thin coating of water to thereby protect the fish from exposure to ambient oxygen.
Finally, the prior art has taught various methods for freezing fish. For nearly a century prior to the filing of this application it has been known to freeze fish and other foods as quickly as possible to prevent formation of ice crystals of a size sufficient to disrupt the cellular walls of the fish; see e.g., Birdseye, U.S. Pat. No. 1,773,080. The various mechanisms of fish decay are also known to be impeded by freezing the fish. For instance, it is known that bacterial metabolic action decreases dramatically as the temperature falls below freezing, and in particular as the temperature drops below 0° F. Certain other rancidity causing reactions, in particular those connected with decay of fats in the fish, can continue until the temperature of the fish drops to −10° F. or below, and thus by cooling the fish, such decay can be avoided.
For a variety of reasons, some related to cost and difficulty and others related to custom and convention, many commercial fisherman have failed to adapt efficient techniques that build on the foregoing knowledge in the art. The present invention seeks to provide, in some embodiments, methods for freezing and for processing fish, which methods, when practiced in preferred form, facilitate and improve upon the prior teachings in the art. In other embodiments, the invention seeks to provide an apparatus that is not only useful in connection with fishing operations but also for numerous other operations, for instance, the freezing of other food products. In another embodiment, the invention seeks to provide a fish stunning apparatus.